Medication Assisted Treatment, with buprenorphine, methadone, or naltrexone, represents the gold-standard intervention for Opioid Use Disorder (OUD) and significantly reduces risk for overdose or death. However, only 20% of Americans with OUD received any formal or informal addiction treatment in the past year. Even in addiction treatment settings, only 32% of patients with OUD received Medication Assisted Treatment. Lack of access and engagement in Medication Assisted Treatment is driving poor OUD outcomes, especially in rural areas lacking specialty addiction services. To close this engagement gap, more patients with OUD need access to Medication Assisted Treatment in primary care settings. Over the last ten years, the Advancing Integrated Mental health Solutions (AIMS) Center at the University of Washington has successfully helped over a thousand primary care clinics across the country implement Collaborative Care for mental health disorders. The proposed study will determine whether Collaborative Care can be used to successfully treat mental health disorders and OUD concurrently in primary care settings. The proposed research addresses three important objectives including: 1) Can OUD screening be effectively incorporated into primary care mental health screening protocols?; 2) Does implementing Collaborative Care for OUD and mental health disorders improve outcomes?; 3) What implementation strategies are effective at sustaining Collaborative Care programs that concurrently manage mental health disorders and OUD? We will recruit 24 clinics from areas with high OUD prevalence from a network of clinics which have previously partnered with the AIMS Center to implement Collaborative Care for mental health. Clinics still offering Collaborative Care will take part in a pragmatic trial that will randomize sites to adding OUD to their Collaborative Care program or maintaining Collaborative Care for mental health disorders. Clinics no longer offering Collaborative Care will take part in a second pragmatic trial that will randomize sites to implementing Collaborative Care for OUD and mental health disorders simultaneously or implementing Collaborative Care for mental health disorders only. Patient reported outcomes will be collected by survey from patients at baseline and at 3- and 6-month follow-up. Process of care data and medication prescription fills for OUD medications will be collected from chart review. Screening for OUD will start at the beginning of each trial at all clinics and electronic health record data will be used to determine if screening improves the detection of new cases of OUD. At the end of the pragmatic trials, the clinics implementing Collaborative care for OUD and mental health will be randomized to receive a low-intensity or high-intensity implementation strategy to promote sustainability. Mixed quantitative and qualitative methods will be used to evaluate these sustainability implementation strategies.